Overlapping homologous superfamilies

Family relationships

Description

ABC transporters belong to the ATP-Binding Cassette (ABC) superfamily which
uses the hydrolysis of ATP to energise diverse biological import and export
systems. ABC transporters are minimally constituted of two conserved regions:
a highly conserved ATP binding cassette (ABC) and a less
conserved transmembrane domain (TMD). These regions can be found on the same
protein (mostly in eukaryotes and bacterial exporters) or on two different
ones (mostly bacterial importers) [PMID: 9873074]. But in a subgroup of exporters, the
transmembrane region is encoded by a separated polypeptide, the ABC-2 type
transport system integral membrane protein. The molecular size of this
transmembrane protein is around 30 kDa. It is thought to contain six
transmembrane regions, it either form homooligomeric channels or associate
with another type of transmembrane protein to form heteroligomers. The
function of the integral inner-membrane protein is to translocate the
substrate across the membrane and seems to play an important role in substrate
recognition [PMID: 10331089].